pub trait ChUtils {
// Required methods
fn is_number(&self) -> bool;
fn is_point(&self) -> bool;
fn is_plus_or_minus(&self) -> bool;
fn is_div_or_prod(&self) -> bool;
fn is_operation_sign(&self) -> bool;
fn is_parentheses(&self) -> (bool, bool);
fn is_abs(&self) -> (bool, bool);
fn is_percentage(&self) -> bool;
}